1. Field of the Invention
The present invention pertains to a multi-interval data acquisition apparatus, and more specifically, one that is designed to enable parallel measurement of measured data at multiple measurement points at measurement intervals which differ according to their respective measurement subjects.
2. Description of the Related Art
In the measurement of, for example, characteristics of a fuel cell system used in electric cars, one may consider simultaneous measurement of fuel cell temperature changes and fluctuations in fuel cell output terminal voltage when starting movement or accelerating, as well as fluctuations in voltage supplied to the various parts of the car's electrical system, and the like. In this case, a measurement interval of, for example, approximately 2 seconds may suffice for temperature changes because they are relatively smooth. However, a measurement interval of, for example, 0.1 second would be required for voltage fluctuations because they occur much more rapidly than do temperature changes, although they are affected by the size of the load's time constant.
Therefore, apparatuses with a configuration such as that shown in FIG. 1, for example, have been commercialized as such multi-point measurement data acquisition apparatuses. If the apparatus in FIG. 1 is considered as a large block, then it is comprised of a main unit 10, which controls the apparatus as a whole; and three input modules 20, 30 and 40 comprising A/D converters, to which respective analog input signals are input via a scanner.
These input modules 20, 30 and 40 have different measurement intervals—low speed, medium speed, and high speed. For example, input module 20 is drive-controlled so as to sequentially measure measurement channels CH1 through CH10 in 2-second measurement intervals. The input module 30 is drive-controlled so as to sequentially measure measurement channels CH11 through CH20 in 1-second measurement intervals. The input module 40 is drive-controlled so as to sequentially measure measurement channels CH21 through CH30 in 0.1-second measurement intervals.
In the main unit 10, the timer 11 manages the time relationships for the apparatus as a whole. In particular, it determines the measurement intervals and applies interrupts to the main control 12.
The main control 12 controls the apparatus as a whole. With respect to measurements, it sends a measurement start command via a command signal line 14 to each of the input modules 20, 30 and 40 according to interrupts from the timer 11; and when measurement ends, acquires measured data from the input modules 20, 30 and 40 via a module data arbitrator 15 and stores the data in the memory 13.
The command signal line 14 has a function for simultaneously sending commands to each of the input modules 20, 30 and 40, in addition to a function for sending with arbitration during command transmission.
The module data arbitrator 15 arbitrates data reception between the main control 12 and each of the input modules 20, 30 and 40. Specifically, it uses a bus line connection system or serial communication to arbitrate the timing of measured data sent from each of the input modules 20, 30 and 40 for sending to the main control 12.
In the input modules, such as in 20, a module control 21 controls the input module 20 as a whole. Specifically, when a measurement start command sent from the main control 12 is received, the module control 21 sends the switch selector 22 a signal for sequentially selecting and driving the switches SW01 through SW10 forming the scanner 23.
The switch selector 22 sequentially selects and drives the switches SW01 through SW10 forming the scanner 23, thereby sequentially and selectively inputting, to the A/D converter 24, the analog signals of each measurement channel CH1 through CH10. Herein, an integrating A/D converter 24, for example, is used.
The A/D converter 24 converts the analog signals input through the scanner 23 to digital signals, which are output to the module control 21 as measured data.
The operations in FIG. 1 will be described using the timing chart in FIG. 2.
The main control 12 simultaneously sends measurement start commands via the command signal line 14 to each of the input modules 20, 30 and 40 in accordance with interrupts from the timer 11.
The main controls of each of the input modules 20, 30 and 40 receiving the measurement start commands start measurement operations, and send their respective switch selectors signals for selecting and driving the lead switches SW01, SW11, and SW21 of the switches SW01 through SW10, SW11 through SW20, and SW21 through SW30 forming the respective scanners.
When the lead switches SW01, SW11, and SW21 of the individual scanners are selected and driven, the A/D converters of the input modules 20, 30 and 40 convert the analog signals of measurement channels CH1, CH11, and CH21 to digital signals, and the conversion results are output as measured data to the main controls of each of the input modules 20, 30 and 40.
The main controls of the input modules 20, 30 and 40 transfer the measured data to the main unit 10.
The module data arbitrator 15 of the main unit 10 arbitrates and receives the measured data sent from each of the input modules 20, 30 and 40, and transfers it to the main control 12.
The main control 12 saves the measured data to the memory 13. When measurement on measurement channels CH1, CH11, and CH21 ends, the switch selectors 22 of each of the input modules 20, 30 and 40 select and drive their second switches SWO2, SW12, and SW22 for measurement of measurement channels CH2, CH12, and CH22.
Subsequently, like processes are executed all the way through CH10. CH20, and CH30 to complete the series of measurements based on the first measurement start command.
Thereafter, when an interrupt from the timer 11 enters at a set measurement interval and a measurement start command is sent, the measurements from (1) through (8) are repeated in the same manner in that interval.
However, with this type of conventional configuration, measurement start commands are sent nearly simultaneously from the main unit 10 to each of the input modules 20, 30 and 40, thereby driving the input modules 20, 30 and 40 to acquire measured data in the same measurement interval.
Consequently, the measurement interval for the apparatus as a whole is the measurement interval of the input module 20 (2 seconds), which is the slowest of the three input modules 20, 30 and 40. This is problematic in that:
It is only possible to perform 2-second measurements, even though an input module 30 with a measurement interval of 1 second and a 0.1-second input module 40 are incorporated. Thus it is not possible to sufficiently realize their capabilities.
Measurements can only be performed at a single measurement interval in the apparatus as a whole, even though it incorporates input modules with multiple intervals.